A strut is a type of damper that is used in vehicle suspensions as both a damping device for providing shock absorbing functions and as part of the suspension's load-bearing structure. Monotube gas-charged dampers are known wherein a piston with a connected piston rod is slidably carried in a fluid-filled tube with a separate piston called a gas cup slidably carried in the tube on an opposite side of the piston from the rod. The gas cup separates a compressible gas charge from the fluid within the damper. It is known that monotube gas-charged dampers exhibit desirable performance characteristics when used in some suspension assemblies.
Typically, the generic monotube strut design configuration is produced primarily as an aftermarket replacement damper, although limited original equipment (OEM) applications have been implemented. The prior art device generally includes a bearing mechanism that includes a combination of a polytetrafluoroethelyne laminated plain bearing and a grease lubricant. In some applications performance advantages of high pressure monotube dampers are well known and therefore, the use of such devices without restriction would be desirable. However, in applying a monotube gas-charged strut in an OEM application, extended durability requirements may lead to restrictions in the use of such devices, particularly in applications involving larger and heavier vehicles that operate with resultant increased side-loading. In particular, such a strut must be assembled and maintained in a straight and true line otherwise, misalignment may lead to premature rod wear and high damper axial friction. Accordingly, it would be desirable to provide a strategy for minimizing rod wear and damper axial friction due to misalignment in a monotube strut.
One strategy developed for minimizing rod wear and damper axial friction in a monotube strut is disclosed in U.S. Pat. No. 6,390,258 to Hofmann et al., which is incorporated by reference herein. The Hofmann patent teaches a floating rod guide assembly including a rod guide, a seal cover, and a retainer. A first O-ring is disposed between the seal cover and the rod guide, and a second O-ring is disposed between the rod guide and the retainer. During operation, a damper rod slides within a passageway provided in the guide assembly. The guide assembly may reduce friction levels and incidence of premature rod wear by compensating for side-load forces exerted on the strut.
Although the guide assembly may effectively reduce friction levels and incidence of premature rod wear with larger side-loads, some wear may occur with smaller side-loads. The prior art strut typically requires that a sufficient side-load is exerted on the assembly to overcome static friction forces associated with the O-rings. Unless the static friction forces are overcome, the rod guide is not free to move laterally to compensate for the smaller side-loads. This may cause binding contact of the piston with other surfaces thereby resulting in premature wear and failure. Accordingly, it would be desirable to provide a floating rod guide that can compensate for smaller side-loads.
Therefore, it would be desirable to provide a floating rod guide that overcomes the aforementioned and other disadvantages.